Captures
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Captures are tactical moves changing material balance where an opponent piece is removed from the board as part of the completion of the move. This is either done by moving a piece to a square, which is occupied by the opponent captured piece - or as a special case of pawn takes pawn, en passant.
Winning captures are those with least valuable aggressor of most valuable victim, where even a recapture would win material, and captures of pieces en prise, that is the union of undefended (hanging) pieces, as well as pieces defended inadequately. A static exchange evaluation might be applied to determine a victim is en prise or not. Equal captures are exchanges of equal valued pieces. Winning, as well as equal captures are subject of quiescence search. Some programs extend captures or recaptures under certain conditions, i.e. material becomes close to the root score again.
Capture Generation
With mailbox like square centric board representations, capture generation requires a so called blocker loop, while bitboards rely on attack generation and intersection with the set of opponent pieces.
Six times Take Five
Capture | Best case | Worst case |
---|---|---|
capturing with the pawn | ||
pxQ | winning queen | pawn for queen |
pxR | winning rook | pawn for rook |
pxB | winning bishop | pawn for bishop |
pxN | winning knight | pawn for knight |
pxP | winning pawn | exchanging pawns |
capturing with the knight | ||
nxQ | winning queen | knight for queen |
nxR | winning rook | winning the exchange |
nxB | winning bishop | exchanging minors |
nxN | winning knight | exchanging minors |
nxP | winning pawn | losing knight for pawn |
capturing with the bishop | ||
bxQ | winning queen | bishop for queen |
bxR | winning rook | winning the exchange |
bxB | winning bishop | exchanging minors |
bxN | winning knight | exchanging minors |
bxP | winning pawn | losing bishop for pawn |
capturing with the rook | ||
rxQ | winning queen | rook for queen |
rxR | winning rook | exchanging rooks |
rxB | winning bishop | losing exchange |
rxN | winning knight | losing exchange |
rxP | winning pawn | losing rook for pawn |
capturing with the queen | ||
qxQ | winning queen | exchanging queens |
qxR | winning rook | losing queen for rook |
qxB | winning bishop | losing queen for bishop |
qxN | winning knight | losing queen for knight |
qxP | winning pawn | losing queen for pawn |
capturing with the king, always winning captures | ||
kxQ | winning queen | |
kxR | winning rook | |
kxB | winning bishop | |
kxN | winning knight | |
kxP | winning pawn |
See also
Forum Posts
- a question about the definition of winning capture in Rebel(diagrams) by Uri Blass, CCC, January 05, 2003
- Reducing/Pruning Bad Captures (SEE < 0) by Edsel Apostol, CCC, August 19, 2011 » Pruning, Reductions, SEE
- Perft and Captures by CDaley11, OpenChess Forum, January 24, 2013 » Perft
- Sorting Captures by David Cimbalista, CCC, August 03, 2016 » Move Ordering
- Ordering Capture Moves by Jason Fernandez, CCC, September 06, 2017 » Move Ordering - Captures